1. Technical Field
The embodiments described herein are related to the use of magnetic fields and imaging with respect to medical procedures, and more particularly to robotic magnetic medicine.
2. Related Art
A wide variety of medical procedures are currently performed with undesirable and unavoidable effects on the patient that include damage to healthy tissue during surgery and distribution of therapeutic substances (drugs, antibodies, vaccines and regenerative cells) to sites other than the intended target. Non-disease related surgery increases the risk of sepsis, scarring, blood loss and decreased motor function. Non-specific therapeutic side effects include impacts on metabolic organs and nervous tissue, undesired accumulation in the liver, fatty tissue and digestive tract, and widespread dilution in the circulatory system.
Many of these effects are unavoidable. In most surgical procedures, a cavity must be created through the skin and sub-derma much larger than the actual lesion. In addition, tools, implants and related devices commonly require large tethers, such as the surgeon's hands, catheters, clamps, etc., for manipulation. For most bio-therapeutics, encapsulation, localization and site-specific delivery are limited because related technology is in its infancy. The vast majority of drugs, antibodies and vaccines depend on molecular specificity to accomplish intended functions and minimize side effects. The latter remains non-optimal due to non-specific substance distribution.
Desired effector functions, e.g., removal of a tumor, clearance of a blocked artery, activation of B or T immune cells, antibody tagging of a specific cell type, etc., are relatively well defined. Unfortunately, procedures that accomplish those effector functions also negative impact healthy tissue. In addition, some avoidable or ameliorable diseases remain because procedures to address them result in collateral damage disproportionate to the amount of benefit. The shared causative factor is that medical technology is currently disadvantaged by an inability to limit operator, electro-mechanical, and biochemical procedures to necessary effector functions.
Current options for therapeutics delivery that attempt to maximize targeting and avoid widespread pharmaco-distribution (PD) include magnetic particles, ligand-coated liposomes and antibody coated micro- or nanoscale capsuled drugs. Work on the latter two have been on-going for decades and focus on two main areas: (1) Encapsulation, including containment of payload during transport to target, assurable release of payload to target, reproducible manufacturing and storage life for regulatory purposes, and (2) Surface functionalization, including engineering of antibodies and ligands for maximal specificity, affinity and avidity to targets, maximal shelf life, pH stability and minimal immunogenicity (immune stealth).
Efforts to incorporate magnetic fields with magnetically susceptible bio-therapeutic laden spheres and colloids have focused on accumulation at the site using permanent magnets or electromagnets positioned at the skin proximal to the target site. Interestingly, magnetic particle thermal effects have been researched, including efforts to elicit tissue damage via antibody or ligand coated particles moving rapidly in pulsating magnetic fields.
The majority of these efforts depend on molecular specificity of effector molecules for target proteins. In rare cases, cancer or viral DNA is targeted but these are early stage efforts. In most cases, critical parameters for determining the efficacy of therapeutics are completely out of operator control after application of the therapeutic, including when, where and how much payload was delivered. The pharmaco-kinetic (PK) question of why an effect or lack thereto occurred often depends on radioactive and other complex and expensive tracing to determine PK/PD.
Even in magnetic, ultrasonic and radio-frequency controlled capsules, conclusions regarding target specification depend on limited biochemical data and broad physical effects, not on the real-time ability to control targeting, application and dosing. In all cases, monitoring of encapsulated payload is not possible except when using magnetic resonance or ultrasonic imaging (MRI, USI) of capsules modified for compatibility with such systems, modifications thereto potentially detrimental to the biotherapeutic payload. Protocols do not yet exist to combine tMRI and USI with both real-time control and accurate targeting of capsules or robotic devices.
More elegant efforts to combine MRI and USI with robotics for drug delivery and surgery include the diverse options of: (1) completely passive or magnetic field-slaved robots having screw or star geometries, and (2) completely autonomous endoscopic devices with on-board computers, propellers, navigation fins, optical cameras and radio-frequency (RF) transmitters. While the latter depend on batteries or, as being researched, RF-based remote energization of on-board power supplies, the former are entirely dependent on external magnetic fields for propulsion. Propulsion-related fields include pulsed attractive or repulsive linear fields, alternating attraction and repulsion gradients produced by orthogonally aligned electromagnetic coils, and rotating fields that impart flagella-like movement. Current endoscopic robots are relatively large and not applicable to vessels and vascular tissue smaller than about 1 cm in diameter. Thus, protocols for cardiovascular, lymphatic and metabolic organs with more narrow vascularization are not possible with current endoscopic robot technology.
In contrast to many medical procedures, dependent technology for medical robots is relatively advanced. Motors, RF transmitters, antennae, microprocessors and even optical detectors can be made on the millimeter [mm] and even micrometer [um] scale. Significant electro-mechanical parameters scale with great linearity from the centimeter [cm] scale, where ubiquitous end products that include servomotors, fans, cameras and mobile phones depend on [mm-um] scale electro-mechanical components. Interest in [mm] scale drone aircraft and gyroscopes, systems also sharing many qualities with ideal medical robots, is high; however, rapid translation of these technologies is hampered by their incompatibility with current MRI and USI systems that only perform diagnosis. Moreover, current MRI technology is incompatible with most robots as well as many implants because of their electrical sensitivity and magnetic susceptibility. Thus, in most cases, diagnosis is maintained separately from therapy.